Unlike an accountant, an economist measures costs on a(n) _____ basis

The correct answer in Option B. replacement.

Technically, the accountants measure the cost at explicit, historical and conservative cost. This is what the management of the company/firm are expected them to do. They are (the accountants) to provide financial reports based on past transactions. On the other hand, an economist uses replacement cost basis which is quite opposite to what an accountant do, like for the analysis of the demand supply functions and equate them to measure the costs.